Internet Engineering Task Force X. Wei
Internet-Draft L. Zhu
Intended status: Standards Track Huawei
Expires: October 3, 2013 April 2013
PAWS Database Discovery
draft-wei-paws-database-discovery-01
Abstract
This document provides a Database Discovery mechanism for PAWS. By
this mechanism the master device gets the available WSDBs with which
it should communicate as well as the regulatory domain information.
The mechanism is based on the LoST protocol .
Status of this Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Motivations . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Mechanism overview . . . . . . . . . . . . . . . . . . . . 3
1.3. Brief introduction of LoST . . . . . . . . . . . . . . . . 4
2. Terminology and Conventions . . . . . . . . . . . . . . . . . 5
3. System Architecture Description . . . . . . . . . . . . . . . 6
4. Specification . . . . . . . . . . . . . . . . . . . . . . . . 9
4.1. Issues to be clarified . . . . . . . . . . . . . . . . . . 9
4.1.1. Service Identifier . . . . . . . . . . . . . . . . . . 9
4.1.2. Conveying of regulatory domain . . . . . . . . . . . . 10
4.1.3. Database administrator information . . . . . . . . . . 10
4.2. Discovery procedures . . . . . . . . . . . . . . . . . . . 10
4.2.1. Discovery Request procedure . . . . . . . . . . . . . 10
4.2.2. Discovery Response procedure . . . . . . . . . . . . . 11
4.2.3. Recursion and Iteration . . . . . . . . . . . . . . . 12
5. Security Considerations . . . . . . . . . . . . . . . . . . . 13
6. IANA Consideration . . . . . . . . . . . . . . . . . . . . . . 13
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
8.1. Normative references . . . . . . . . . . . . . . . . . . . 13
8.2. Informative References . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
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1. Introduction
1.1. Motivations
In the PAWS protocol, the master device queries the database for
available spectrum, but the device MUST determine the URL for the
database before it can send any PAWS messages. Brief discussions of
database discovery can be found in [PAWS RQMTS] and [PAWS PROTOCOL].
Several different choices can be taken for the device to determine
the appropriate URL(s) for connection. There are some possible
methods for this purpose (not all methods are included here): (1) the
manufacturer or the user of device can manually pre-configure
statically the URL(s) of one or more databases that is available for
the device to query white space spectrum (e.g. the device and
database have agreements with each other.), for example, if the
device is to be used in US, it will be configured with the database
of US, and then it directly connects to the database in US, or if the
device is to be used in several countries it can be configured with
different database for each country ; (2) or the device can be
configured by certain provisioning process after attaching to
operator's network.
But in some scenarios the methods above may not work well. For
example, to pre-configure a device, the user has to know the
available database(s) that can be used in the regulatory domain, and
it may be inconvenient to do so especially when the device is moved
to a different regulatory domain. So a dynamic database discovery
mechanism is provided here, and the mechanism can be used
independently or cooperate with other methods, e.g. device can first
connect to the configured or provisioned databases, if that fails
then the device can use the dynamic mechanism to find out available
databases.
Besides, it is possible that some databases are not available any
more or some new databases are setup, the pre-configuring and
provisioning method may not cope with it very well.
The mechanism discussed in this memo will be provided as an OPTIONAL
method as described in PAWS PROTOCOL [PAWS PROTOCOL].
1.2. Mechanism overview
The dynamic database discovery mechanism provided here is used by a
device to discover the available white space databases for its
current location and related regulatory domain information.
In the discovery procedure, the URL for the database SHOULD be
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obtained from an authorized and authenticated entity. The master
device provides its current geo-location information to the entity in
a Database Discovery Request message, and the entity will return a
list of available databases and the regulatory body that has
jurisdiction over the master device's location.
When the master device gets the information about available database
and regulatory body, it can choose the proper database for querying
white space spectrum by PAWS procedures.
The database discovery mechanism is based on LoST protocol [RFC5222].
1.3. Brief introduction of LoST
LoST (Location-to-Service Translation Protocol) is an XML-based
protocol for mapping service identifiers and geodetic or civic
location information to service contact URLs.
+-----------+ +-----------+
|LoST Client| |LoST Server|
+------.----+ +------.----+
| |
| Request(Location info,service id) |
|------------------------------------->|
| |
| +---------------------------------+
| |Mapping location and serivice id |
| |
| | to service URL(s) |
| +---------------------------------+
| |
| Response(Service URL(s)) |
| <----------------------------------- |
| |
| |
| |
| '
Figure 1: An overview of procedures in LoST protocol
The LoST client sends its location information and service type it
wants to LoST server to retrieve one or more service URLs.
The LoST server maintains the mapping relationship between location
and service URL, and on receiving request message it maps the
location and service identifier in the request to one or more service
URLs that can offer the service in the location.
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LoST can operate in either recursive or iterative mode, on a request-
by-request basis. In recursive mode, the LoST server initiates
queries on behalf of the requester and returns the result to the
requester.
In iterative mode, the server contacted returns a redirection
response indicating the next server to be queried if the server
contacted cannot provide an answer itself.
2. Terminology and Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [RFC2119].
The terminology from PAWS: problem statement, use cases and
requirements PAWS RQMTS [PAWS RQMTS] is applicable to this document.
White Space Database (WSDB)
In the context of white space and cognitive radio technologies, the
database is an entity which contains, but is not limited to, current
information as required by the regulatory policies about available
spectrum at any given location and time, and other types of related
(to the white space spectrum) or relevant information.
White Space Database Discovery Server (WSDB DS)
A server function provided to a white space device, the client. The
white space device contacts a white space database discovery server
to receive the service of discovering or identifying one or more
white space databases. The white space database discovery server is
a known entity to the white space device, which knows at least a
useable internet address for the white space database discovery
server. The white space database discovery server takes as input
positioning information from the white space device and returns both
URLs of white space databases that cover white space device's current
location and indication of the regulatory domain governing at the
white space device's current location. A single white space database
discovery server may have global scope, serving clients located
globally.
Service boundary
A service boundary circumscribes the region within which all
locations map to the same service URL or set of URLs for a given
service. A service boundary may consist of several non-contiguous
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geometric shapes.
Mapping
Mapping is a process that takes a location and a service identifier
as inputs and returns one or more URLs. Those URLs can point either
to a host providing that service or to a host that in turn routes the
request to the final destination.
Device
The device in this memo is equivalent to the master device described
in PAWS RQMTS [PAWS RQMTS].
3. System Architecture Description
Before the WSD can query a trusted WSDB for a list of available
frequencies or channels for use in the white space spectrum, the WSD
must first discover the available databases and addresses serving the
regulatory domain in which the device is currently located. At
power-up the WSD does not reliably know the regulatory domain
corresponding to its current location, and therefore does not
reliably know with which white space database(s) it can communicate.
Furthermore it is essential that the WSD connect with a trusted WSDB
for proper operation and indeed regulatory compliance.
The discovery system is based on client-server model; the basic model
is shown in Figure 2, where WSDB DB (WSDB Discovery Server) plays the
role of LoST server and Master device acts as LoST client.
+----------+ +----------+
| Master | <--------> | WSDB DS |
+----------+ +----------+
Figure 2: DB discovery system model
The WSDB DS takes as input location information from the WSD and
returns to the WSD one or more addresses of WSDBs (or WSDB listing
servers as appropriate) to the WSD.
For the discovery mechanism to work well, some assumptions have to be
considered:
(1) Master device can get its geo-location directly or indirectly.
(2) Master device has gotten the URL (or IP address) of a trusted
WSDB DS before starting the discovery procedure.
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The URL or IP address of WSDB DS can be found by any method such as
DNS, DHCP, manually configuring etc, and it is out of scope of this
document.
When the WSD does not have the address of a serviceable WSDB (e.g. at
power-up), the WSD sends a Discovery Request message to a WSDB DS.
The WSD includes in the Discovery Request information about its
current location. The WSDB DS uses this location information to
determine the regulatory domain where the WSD is located, and returns
a Discovery Response message which includes the address of one or
more WSDBs (or WSDB listing server as appropriate) to the WSD.
An overview of procedures of how master device gets available
spectrum from WSDB is depicted in Figure 3.
+-----------+ +-----------+ +----------+
| | | WSDB | | |
| WSD | | Discovery | | WSDB |
| | | Server | | |
+-----------+ +-----------+ +----------+
| | |
| Discovery Request | |
|(location information, etc) | |
|--------------------------->| |
| | |
| Discovery Response | |
| (address information, etc) | |
|<---------------------------| |
| | |
| | |
| /--------------------------|-----------------------\ |
|/ | \|
|\ | (PAWS) /|
| \--------------------------|-----------------------/ |
| | |
| | |
Figure 3: An overview of procedures of how master device gets
available spectrum from WSDB
(1) Discovery Request procedure. This message is used by master
device to query available WSDB from WSDB DS; it conveys master's
location and some other related information to WSDB DS.
(2) Discovery Response procedure. This procedure conveys the
regulatory domain and either the address of a listing server or the
address of one or more WSDB authorized to provide service where the
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WSD is physically located to the master device. If spectrum access
is not authorized at the WSD physical location, the response will
contain an error code and no address information.
(3) After WSDB discovery procedure, the master device can query
available white space spectrum from the WSDB using PAWS protocol.
Figure 4 shows at a high level how white space master devices
discover a suitable trusted white space database. In this document
we describe how the master device may collect the addresses of one or
more white space database. Procedures to contact a white space
database are specified in PAWS PROTOCOL. [PAWS PROTOCOL]
+------+ +-------+
|Master| |WSDB DS|
+---+--+ +---+---+
| |
| Request(location,service id) |
------------------------------------>|
| |
| Response(a list of URLs of DB) |
|<-----------------------------------|
| |
+----------------------------------------+ |
|Select an available DB that can be used | |
| by master to query for white space | |
+----------------------------------------+ |
| |
| |
| |
Figure 4: High level view of white space database discovery
In the response message a list of databases that cover the location
are included, when a database is included, it only means the location
is in its coverage range but not means the master device can get
service from the database, because the database may need the master
device has service agreement or some other relationship with it. So
master device needs to select an available database from the database
list.
After master device has selected a available database for service, it
can then use the PAWS protocol PAWS PROTOCOL [PAWS PROTOCOL] to
retrieve the available spectrum for its location.
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4. Specification
LoST (Location to Service Translation Protocol) is a protocol for
mapping a service identifier (URN) and location information to one or
more service URLs and associated information. LoST mapping queries
can contain either civic or geodetic location information. LoST
queries can be resolved recursively or iteratively.
LoST messages are carried in HTTP and HTTPS protocol exchanges,
facilitating use of TLS for protecting the integrity and
confidentiality of requests and responses.
This discovery mechanism utilizes LoST to communicate between master
device and WSDB DS, the master device acts as LoST client and WSDB DS
plays the role of LoST server. The protocol stack is shown in Figure
5. To use LoST for this discovery mechanism, several issues have to
be clarified.
+------------+
| LoST +
+------------+
| HTTPS +
+------------+
| TCP +
+------------+
| IP +
+------------+
Figure 5: Protocol stack for discovery mechanism
4.1. Issues to be clarified
4.1.1. Service Identifier
A new service identifier for PAWS database discovery needs to be
defined, according to RFC5031 [RFC5031], a top-level service and a
sub-service are defined here.
+----------------+-------------------------------------+
| Service | Description |
+----------------+-------------------------------------+
| paws | top-level service of PAWS |
| paws.discovery | the PAWS database discovery service |
+----------------+-------------------------------------+
Table 1
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So according to the service-identifying labels defined above, the
service URN for PAWS database discovery service is as follow:
urn:service:paws.discovery
4.1.2. Conveying of regulatory domain
The name of regulatory domain can be conveyed using <displayName>
element in the LoST response message.
[Note: the format and content of the regulatory domain information
are TBD.]
4.1.3. Database administrator information
The WSDB DS can return one or more databases to master device, but
because the databases are in the form of URL so it may be difficult
to decide which one has service agreement with the master device.
Here an extension to LoST is needed: for every <URL> element that
used for conveying URL a new attribute (admin) which contains the
database's administrator information needs to be added.
Based on the newly added attribute master device can choose the
database that it has agreement with.
4.2. Discovery procedures
4.2.1. Discovery Request procedure
The discovery request procedure uses the <findService> query message
of LoST for conveying parameters. Master device's location
information will be included in the <location> element.
The service identifier defined in Section 4.1.1 is specified in the
<service> element.
The following is an example of discovery request procedure message,
using geodetic coordinates.
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<?xml version="1.0" encoding="UTF-8"?>
<findService
xmlns="urn:ietf:params:xml:ns:lost1"
xmlns:p2="http://www.opengis.net/gml"
serviceBoundary="value"
recursive="true">
<location id="6020688f1ce1896d" profile="geodetic-2d">
<p2:Point id="point1" srsName="urn:ogc:def:crs:EPSG::4326">
<p2:pos>37.775 -122.422</p2:pos>
</p2:Point>
</location>
<service>urn:service:paws.discovery</service>
</findService>
4.2.2. Discovery Response procedure
The discovery response procedure uses the <findServiceResponse>
response message of LoST for conveying parameters.
After receiving the <findService> query message, the WSDB DS will map
the location information and service identifier to one or more
available WSDBs' URL.
Then in the <findServiceResponse> message, a list of WSDBs' URL and
regulatory domain that has jurisdiction over the current location
will be conveyed to master device. The regulatory domain is
contained in <displayName> element.
The service boundary of the WSDB can also be included in the response
message to indicate the region for which the service URL returned
would be the same as in the actual query. Or a service boundary
reference can be returned to master device, and master device
retrieve service boundary by this reference as needed. Next time
when the master device powers up, if its location is within the
service boundary it then may use the WSDB retrieved before.
An example of discovery response procedure message is shown as
follow:
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<?xml version="1.0" encoding="UTF-8"?>
<findServiceResponse xmlns="urn:ietf:params:xml:ns:lost1"
xmlns:p2="http://www.opengis.net/gml">
<mapping
expires="2013-05-01T01:44:33Z"
lastUpdated="2012-11-01T01:00:00Z"
source="authoritative.example"
sourceId="7e3f40b098c711dbb6060800200c9a66">
<displayName xml:lang="en">
Federal Communications Commission
</displayName>
<serviceBoundary profile="geodetic-2d">
<p2:Polygon srsName="urn:ogc:def::crs:EPSG::4326">
<p2:exterior>
<p2:LinearRing>
<p2:pos>37.775 -122.4194</p2:pos>
<p2:pos>37.555 -122.4194</p2:pos>
<p2:pos>37.555 -122.4264</p2:pos>
<p2:pos>37.775 -122.4264</p2:pos>
<p2:pos>37.775 -122.4194</p2:pos>
</p2:LinearRing>
</p2:exterior>
</p2:Polygon>
</serviceBoundary>
<service>urn:service:paws.discovery</service>
<uri admin="admin1">database1.example1.com</uri>
<uri admin="admin2">database2.example2.com</uri>
</mapping>
<path>
<via source="resolver.example"/>
<via source="authoritative.example"/>
</path>
<locationUsed id="6020688f1ce1896d"/>
</findServiceResponse>
4.2.3. Recursion and Iteration
If the WSDB DS can not provide available WSDB for master device, then
it may wish other WSDB DS to serve the master device's query request.
In LoST, recursion and iteration patterns are provided for this
purpose.
In recursive mode, the LoST server initiates queries on behalf of the
requester and returns the result to the requester.
In iterative mode, the server contacted returns a redirection
response indicating the next server to be queried if the server
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contacted cannot provide an answer itself.
5. Security Considerations
TBD.
6. IANA Consideration
Registration of service URN for PAWS database discovery service.
+----------------+-------------------------------------+
| Service | Description |
+----------------+-------------------------------------+
| paws | top-level service of PAWS |
| paws.discovery | the PAWS database discovery service |
+----------------+-------------------------------------+
Table 2
7. Acknowledgements
Thanks to my colleagues for their sincerely help and comments when
drafting this document.
8. References
8.1. Normative references
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5031] Schulzrinne, H., "A Uniform Resource Name (URN) for
Emergency and Other Well-Known Services", RFC 5031,
January 2008.
[RFC5222] Hardie, T., Newton, A., Schulzrinne, H., and H.
Tschofenig, "LoST: A Location-to-Service Translation
Protocol", RFC 5222, August 2008.
8.2. Informative References
[PAWS PROTOCOL]
Chen, V., Das, S., Zhu, L., McCann, P., and J. Malyar,
"Protocol to Access Spectrum Database",
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draft-ietf-paws-protocol-01 (work in progress),
December 2012.
[PAWS RQMTS]
Probasco, S. and B. Patil, "Protocol to Access White Space
database: PS, use cases and rqmts",
draft-ietf-paws-problem-stmt-usecases-rqmts-12 (work in
progress), January 2013.
Authors' Addresses
Xinpeng Wei
Huawei
Phone: +86 134 3682 2355
Email: weixinpeng@huawei.com
Lei Zhu
Huawei
Phone: +86 139 1015 7020
Email: lei.zhu@huawei.com
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